Can I accelerate the time of the island scan?

The way you've worded your question appears to be such that you are asking whether or not you can scan enough QR codes to be able to do an island scan more than once every 2 hours.

To that end, yes, you are able to do up to 2 island scans in a short period of time. The only way to do this is to scan 10 QR codes (or however many you need to have 100 points from QR scans), then wait for you to be able to scan 10 QR codes again.

Once all of your QR scans have been replenished, you could do an island scan, catch the Pokemon you want, then immediately scan 10 more QR codes and perform another island scan.

Unfortunately, you are not able to speed up the replenishment speed of your QR scans in any way. From Serebii, you will replenish your scans at a rate of 1 per every 2 hours.